*{
    margin: 0;
    padding: 0;
}
h2{
    text-align: center;
}
.main{
    width: 1200px;
    margin: auto;
}
.main1{
    background: lightpink;
    height: 100px;
    float: left;
    width: 33.3333333%;
    text-align: center;
}
.main::after{
    content: "";
    display: block;
    clear: both;
}
@media (max-width: 600px){
    .main{
        width: 100%;
    }
    .main1{
        width: 100%;
        background: lightgreen;
    }
}